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From: Jeff King <peff@peff.net>
To: ZheNing Hu <adlternative@gmail.com>
Cc: Git List <git@vger.kernel.org>
Subject: Re: [PATCH 1/2] ref-filter: hacky "streaming" mode
Date: Thu, 16 Sep 2021 17:45:02 -0400	[thread overview]
Message-ID: <YUO63qy2/5wibY4/@coredump.intra.peff.net> (raw)
In-Reply-To: <CAOLTT8SYxUbfG7YvAs03nwRdee8JfNPUYCCpKcFoAgBjB2oqLw@mail.gmail.com>

On Wed, Sep 15, 2021 at 10:23:43PM +0800, ZheNing Hu wrote:

> ZheNing Hu <adlternative@gmail.com> 于2021年9月15日周三 下午8:27写道:
> >
> > > So yes, it's complicated. And it must be explained to the user that
> > > "%(refname)" behaves slightly differently with "git tag --verify", but
> > > that is unavoidable if we do not want to break scripts (it _already_
> > > behaves slightly differently, and we just never told anyone).
> > >
> 
> $ git tag --verify --format='verify: %(refname) %(symref)' annotated symref
> verify: annotated
> verify: symref
> $ git tag --verify --format='verify: %(refname) %(symref)'
> refs/tags/annotated refs/tags/symref
> error: tag 'refs/tags/annotated' not found.
> error: tag 'refs/tags/symref' not found.

This is expected. When you provide a tag name on the command line of
"git tag" it is assumed to be a non-qualified name in refs/tags/ (and
ditto for git-branch and refs/heads/). It is tempting to try to be
friendly and accept fully-qualified refs there, but it would create
ambiguities (e.g., you could really have refs/tags/refs/tags/foo as a
ref).

I think we can ignore that for our purposes here, though. It's a
question of input from the command-line, and we focus on just the output
that we produce.

> $ git verify-tag --format='verify: %(refname) %(symref)' annotated
> symref
> verify: annotated
> verify: symref
> $ git verify-tag --format='verify: %(refname) %(symref)'
> refs/tags/annotated refs/tags/symref
> verify: refs/tags/annotated
> verify: refs/tags/symref
> 
> As we can see, there is a slight difference between git tag --verify and
> git verify-tag: git tag --verify can not handle refs' fullname refs/tags/*
> (because read_ref_full() | read_ref() can't handle them). So, as a standard,
> which characteristics should we keep?

Whereas are you notice here, verify-tag takes any name (which could be
fully qualified), and uses it as-is. In fact, it might not even be a ref
at all! You can say "git verify-tag c06b72d02" if you want to. And as a
plumbing tool, we should make sure this continues to work. For example,
careful scripts may resolve a ref into an object, and want to continue
talking about that object without worrying about the ref being changed
simultaneously.

But it also creates a weirdness for "git verify-tag --format". We do not
necessarily even have a ref to show. So IMHO the feature is somewhat
mis-designed in the first place. But we should probably continue to
support it as best we can.

The best I can come up with is:

  - when we resolve the name, if it was a ref, we should record that.
    I think this is hard to do now. It would probably require
    get_oid_with_context() learning to report on the results it got from
    dwim_ref().

  - if we have a refname, then feed it to pretty_print_ref() as a
    fully-qualified name. And pass whatever "default lstrip=2" magic we
    come up with for "git tag --verify". That would mean that "git
    verify-tag --format=%(refname) v2.33.0" would behave the same before
    and after.

  - if we didn't get a refname, then...I guess continue to pass the name
    the user gave us into pretty_print_ref()? That would keep "git
    verify-tag --format=%(refname) c06b72d02" working as it does today.

The alternative is to do none of those things, and just document that
"verify-tag" is weird:

  - its %(refname) reports whatever you gave it, whether it is a ref or
    not

  - some advanced format placeholders like %(symref) may not work if you
    don't pass a fully-qualified ref

-Peff

  reply	other threads:[~2021-09-16 21:45 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-04 12:40 [hacky PATCH 0/2] speeding up trivial for-each-ref invocations Jeff King
2021-09-04 12:41 ` [PATCH 1/2] ref-filter: hacky "streaming" mode Jeff King
2021-09-05  8:20   ` ZheNing Hu
2021-09-05 13:04     ` Jeff King
2021-09-07  5:28       ` ZheNing Hu
2021-09-07 18:01         ` Jeff King
2021-09-09 14:45           ` ZheNing Hu
2021-09-10 14:26             ` Jeff King
2021-09-15 12:27               ` ZheNing Hu
2021-09-15 14:23                 ` ZheNing Hu
2021-09-16 21:45                   ` Jeff King [this message]
2021-09-20  7:42                     ` ZheNing Hu
2021-09-16 21:31                 ` Jeff King
2021-09-05 13:15     ` Jeff King
2021-09-07  5:42       ` ZheNing Hu
2021-09-04 12:42 ` [PATCH 2/2] ref-filter: implement "quick" formats Jeff King
2021-09-05  8:20   ` ZheNing Hu
2021-09-05 13:07     ` Jeff King
2021-09-06 13:34       ` ZheNing Hu
2021-09-07 20:06       ` Junio C Hamano
2021-09-05  8:19 ` [hacky PATCH 0/2] speeding up trivial for-each-ref invocations ZheNing Hu
2021-09-05 12:49   ` Jeff King
2021-09-06 13:30     ` ZheNing Hu
2021-09-07 17:28       ` Jeff King
2021-09-09 13:20         ` ZheNing Hu
2021-09-06  6:54 ` Patrick Steinhardt

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